Proliferation of Smooth Muscle Cells at Sites Distant from Vascular Injury

This study Investigated the phenomenon that Injury at one specific site In blood vessels Induces cell replication at distant vascular sites. A polyethylene tube was Inserted via the common carotid Into rat aortic arch, which caused focal endothellal cell loss and formation of platelet thrombi. In a similar fashion, a polyethylene tube was placed Into the lower abdominal aorta via a femoral artery. All animals received 3H-thymldlne continuously for 2 weeks, after which time segments of the aorta distant from the polyethylene tubing were processed for autoradlography. These sites showed no loss of endothelium or adherent platelets, and yet the smooth muscle and endothellal cell replications were significantly elevated as compared to control aortas. There was no significant change In blood pressure during these experiments and no Increase In smooth muscle cell ploldy. When the polyethylene tubing was left In situ for 2 months, no Increased replication of the smooth muscle cells was observed during the last 2 weeks of the experiment, and at this time the aorta adjacent to the tubing was completely re-endothellaltzed. Finally, the mltogenlc activity of plasma from these animals was tested in vitro. At the time of a significant Increase of In vivo cel